Compact thermochemical reactor with optimised transfers and maintenance

ABSTRACT

A device for heating and/or cooling a medium contained in a compartment, includes a reactor, a reservoir containing a fluid able to change states in a determined temperature and pressure range, and elements for circulating gaseous fluid between the reactor and the reservoir, a rigid enclosure that contains a reactive medium able to absorb and desorb the fluid in the gaseous state through a thermochemical reaction, elements for diffusing the gaseous fluid in and from the reactive medium, heat transfer elements between the reactive medium and the outside medium. The enclosure of the reactor is formed from two bodies assembled by a peripheral flange, at least the first of which adopts the general shape of a cap with a circular or quasi-circular straight section that contains the reactive medium in the form of at least one block hugging the general shape of the cap.

The present invention belongs to the field of apparatus for transferring and storing thermal energy and more particularly that of the thermochemical reactors with which such apparatus is equipped.

The subject of the present invention is an apparatus for heating and/or cooling a compartment, that uses the alternating phases of absorption and release of heat of a chemical system contained in a reactor as a result of its changes of state, the reactor having a structure that can easily be dismantled and that encourages exchanges of heat.

It is known practice to use thermochemical systems to produce cold and/or heat. These systems are based on the thermal variations that result from physicochemical transformations of a pair of compounds that are able to interact with one another. Typically, one of the compounds is a fluid and the other compound is formed of reactive salts that combine with the fluid when brought into contact at a given temperature, but which dissociate from one another when the temperature increases.

The fluid may be gaseous or liquid according to the temperature and pressure conditions to which it is subjected. In the systems of interest here, it is kept in the liquid state in a reservoir which is separated by a valve from the reactor containing the reactive salts. When the valve is opened, the fluid undergoes an expansion during which it vaporizes and will react chemically with the salts. The change in state of the fluid (from liquid to gaseous) consumes energy and therefore leads to a drop in temperature at the reservoir. On the other hand, the chemical reaction between the gas and the salts is exothermal and causes heat to be released in the reactor. In the state of equilibrium, after all of the fluid has vaporized or when the salts have become saturated, the chemical reaction stops as do the production of cold and of heat.

It is then possible to regenerate the system by heating the reactive salts, something which causes the salts and gas to separate. As a result, the pressure in the system is seen to increase and the gas is seen to condense, returning to the liquid state in the reservoir. The salts thus regenerated are able to react in a further refrigeration-heating cycle.

It is known practice to use the alternating heat-producing and heat-absorbing phases of such a system as need be for heating or cooling a compartment with which it is associated via a thermally conductive device (heat pipe).

Such a method is known for example from document FR 2 873 793 which describes the coupling of a process involving the phase transition of a fluid such as ammonia NH3 (using evaporation and condensation) with a highly exothermal chemical reaction whereby the gaseous fluid is absorbed by a reactive solid such as salts and notably calcium chloride CaCl₂ or barium chloride BaCl₂, etc. The essential point is that this reaction is reversible and heating allows the salts to be regenerated and the initial gas to be recovered (desorption of the gas).

The intrinsically discontinuous and cyclic operation of the thermochemical process is well suited to the functions of transformation and storage of an intermittent and recurrent energy such as the solar energy collected by flat or tubed thermal collectors. In this case, the method is conventionally applied in two main reaction phases carried out under different thermodynamic conditions: a diurnal phase of regenerating the reactive salts by desorption of and of storing the energy produced, followed by a nocturnal phase of cold production.

During the diurnal phase, the energy delivered by the solar collectors is used to heat the reactor and decompose the solid reagent which releases the refrigerating gas which then condenses in a condenser kept at the external ambient temperature. When there is a surplus of solar energy, this energy can be stored for example in a phase-change material for later use, for example for a more rapid heating of the reactor the following morning, or for some other use such as for producing hot water.

The nocturnal cold-production phase consists in cooling the reactor at the end of the day so that it chemically reabsorbs the gas originating from the evaporation of the fluid in the reservoir, thus producing cold. The cold produced in the reservoir can be used directly to cool the compartment of a given medium, and the heat produced in the reactor by the exothermal reaction can also be used directly to heat a compartment of a given medium. These (cold or hot) energies may also be stored in phase-change materials in order to be delivered later according to demand.

Various experiments have allowed the solar collection efficiency to be evaluated at around 50% and to evaluate the coefficient of performance (COP) of the process at 40%, meaning that around 20% of the incident solar energy can be converted directly into cold using such a thermochemical device. Note that heat sources other than solar energy can be used for the regeneration phase, for example geothermal energy or free heat derived from industrial processes, electricity power stations or exhaust gases from combustion engines. In that case, studies lead to an overall efficiency estimated as being in the order of 35 to 40%.

The practice and economic benefit that such a system may offer for supplying energy to isolated regions or regions with poor connections to the electricity networks, but also for optimizing energy consumptions, will therefore be understood.

Implementation of the system thus defined does, however, require suitable equipment. Specifically, the thermochemical reaction involves high pressures, which dictates that the reactors need to have high mechanical strength in order to meet the requirements of the reaction. They need to be perfectly sealed against gases and against liquids and also be resistant to corrosion from the compounds involved. This is why they are generally made of strong material such as steel, and particularly stainless steel, or from composite materials.

For the same reasons, reactors hitherto known have been of cylindrical overall shape closed at each of their ends by a fixed wall welded to the cylindrical body or formed as one therewith. They are fitted with gas diffusing means that place the reactive medium in communication with the reservoir containing the fluid and allow the gas to circulate in one direction or the other according to the reaction phase. They are also provided with means for heating the reactive medium, which means will be set into operation for desorbing the gas and regenerating the reactive salts. Furthermore, the reactors are generally equipped with a ventilation system intended to ensure rapid cooling of the reactive medium at the end of the regeneration phase.

Because of the cylindrical shape of the reactors, these various means and the ancillary accessories used for performing the functions of supplying and circulating gases, filtering, cooling and heating, etc. are advantageously placed in a sleeve, again cylindrical, placed at the center of the reactor along the longitudinal axis thereof (or sometimes in several sleeves arranged around a central sleeve). As an alternative, the heating elements may be arranged as bands around the reactor, but in that case, the insulating nature of the structural materials, steels in particular, represents an obstacle to the heat transfer.

Document FR 2 966 572 for example describes a tube-shaped reactor in which the ends are closed by hemispherical or hemi-ellipsoid walls (integrated geometry in the case of a reactor made of composite material or geometry with welded-on domed ends in the case of a reactor made of steel). The heating of the reagents in the regeneration phase is performed using a resistive electrical element (of the immersion heater type for example) placed in a sleeve deep within the cylindrical body. The tubings and various connecting means essential for carrying out the ancillary functions are passed through orifices made in the end walls and equipped with devices that are sealed through welding or screwing.

An arrangement of this type is well suited when use is made of electrical means for heating the reactor, whether this be a resistive heating means of the immersion heater type or in the form of a heater band. However, this has numerous disadvantages.

A first disadvantage stems from the difficulty in maintaining these systems, particularly when it is necessary to access the inside of the reactor. Specifically, because the reactor is sealed by welding, or may have only very small size orifices, as set out in FR 2 966 574, access to the internals of the vessel and to the reactive medium entails cutting the reactor, and this is of necessity a major intervention involving extremely technical means. Likewise, the creation of connections that are sealed and resistant to the mechanical, thermal, chemical stresses, etc. between the reactors and the various heating, filtering, gas communication, etc. devices are complex and expensive operations that it is desirable to avoid as far as possible.

On the other hand, it is not really realistic to hope to be able to avoid regular maintenance, on the one hand because of the nature of the reactive medium and on the other hand because of the intense stresses that the components of the reactor and the reactor itself experience, which cannot fail to lead to regular degradation.

Indeed the reactive medium present in the reactor is commonly made of an expanded natural graphite (ENG) matrix in which the reactive salt is inserted prior to compression. This composite reactive medium releases particles which may be drawn out when the reactor is placed in communication with the reservoir. In order to avoid plugging the transfer circuit, the reactors need to be fitted with filtering means, but these in turn are liable to clogging. Now, replacing them involves opening the sealed body of the reactor and, especially, closing it again after the components have been unclogged or replaced, and this is a tricky and complex operation.

Moreover, because the thermochemical reaction is reversible, the successive phases of absorbing or desorbing the gas give rise to an alternation of expansion and contraction of the composite porous matrix which, ultimately, leads to phenomena of clogging and compaction of the reactive medium. The only solution is then to replace the reactive medium, something which likewise entails opening the reactor.

Another disadvantage of the known systems stems from the cylindrical design of the reactors in which the length/diameter ratio is of the order of 4 to 5, thereby limiting the surface areas for contact and exchange of heat with the reactive medium. This is clearly suboptimal from the standpoint of controlling the fluid absorption and desorption processes.

An analysis of the thermochemical systems indeed shows that there is a direct relationship between the temperature and pressure of equilibrium of the reaction, on the one hand, and between the liquid/gas states of equilibrium on the other. Hence, it is particularly desirable to provide uniform and even heating of the reactive medium and of the vessel of the reactor during the regeneration phase. It is also important to be able to obtain uniform, even, yet rapid, cooling of the reactive medium and of the vessel of the reactor at the end of the regeneration phase, because the cold-production phase needs to start at the end of this high-temperature phase and will be all the more efficient if it is carried out at low temperature. Added to this need for cooling at the end of the regeneration is a need for cooling during the absorption phase, the purpose of this being to shift the point of equilibrium of the reaction.

In the conventional systems, the cooling function is generally performed by an electric ventilation system which allows only limited and spot cooling, and furthermore introduces a rotary component into the device, this being a sensitive component that may present problems, especially in a harsh environment.

Therefore this solution is unsatisfactory.

In order to address this problem, it has been proposed that the length/diameter ratio of the reactor be increased. This allows better diffusion of the gas in the reactive matrix, especially since, for a composite reactive medium based on ENG and on salts, mass transfers (of gas) and heat transfers (cooling of the reactive medium in the absorption phase and heating thereof in the regeneration phase) take place more readily in a radial rather than longitudinal direction. This well known phenomenon can be explained by the fact that graphite has a layered structure which is responsible for the anisotropy of all the physical properties of graphite. In particular, its thermal conductivity in the plane of the layers and in the perpendicular direction are very different. According to the industrial process most commonly used when manufacturing the graphite/salts composite matrix, a mixture of ENG granules and of salts is compressed in a cylindrical mold, and this orientates the layers of graphite in a plane perpendicular to the direction of the compression, the reactive salts becoming intercollated in the space left between them. The layers thus formed in the reactive medium thus find themselves oriented in planes perpendicular to the longitudinal axis of the reactor, something that will encourage radial thermal conductivity.

Increasing the length of the cylindrical reactors meets these criteria, but on the other hand has a negative impact on the compactness of the reactor. Admittedly, several shorter reactors can be combined in order to limit overall size while at the same time maintaining the desired power of the overall system, but multiplying the number of reactors also multiplies the cost of equipment and the maintenance operations.

It is an object of the present invention to overcome these disadvantages by proposing a thermochemical system the manufacture and operation of which are easier while at the same time offering performance that is the equal of, if not superior to, the systems hitherto known. In particular, one objective of the invention is to offer a reactor with the ancillary components thereof that has a design such that the manufacturing, assembly and maintenance operations become easier. It is another object of the invention in particular to allow rapid dismantling and easy access to all the internal components.

In order to meet these objectives, an apparatus has been designed in which the reactor vessel that contains the reactive medium is formed of two bodies assembled by a peripheral flanged connection, of which bodies at least the first adopts the overall shape of a cap of circular or near-circular cross section. This then yields a spherical (or hemispherical) reactor of which the vessel is formed by the assembly of two bodies using a peripheral flanged joint. As a result, it is easy to dismantle and to reassemble. It may also be dimensioned for high heat exchange powers, given that its geometry encourages a uniform stress distribution.

More specifically, the subject of the present invention is an apparatus for heating and/or cooling a medium contained in a compartment external to said apparatus, comprising i) a reactor, ii) a reservoir containing a liquid or gaseous fluid capable of changing state in a determined range of temperatures and of pressures, and iii) means of circulating the gaseous fluid between the reactor and the reservoir, said reactor comprising:

-   -   a rigid enclosure defining a vessel which contains a reactive         medium able to absorb and desorb said fluid in the gaseous state         through a thermochemical reaction,     -   diffusing means for diffusing said gaseous fluid into and from         said reactive medium,     -   heat-transfer means for transferring heat between said reactive         medium and said external medium,         the apparatus being characterized in that the enclosure of the         reactor is formed of two bodies assembled by a peripheral         flanged joint, the first of which bodies at least adopts the         overall shape of a cap of circular or near-circular cross         section which contains said reactive medium in the form of at         least one block conforming to the overall shape of said cap.

The overall structure of the apparatus according to the invention may be that of the known apparatus. In particular, the reservoir containing a fluid capable of changing state within the range of operating temperatures and pressures of the apparatus may be carefully chosen or designed by the person skilled in the art. The fluid is often referred to as refrigerant insofar as it is the expansion phase in which it consumes energy that is used first and foremost in the apparatus according to the invention (and also in other devices such as refrigerators). Likewise, the means of circulating the gaseous fluid between the reactor and the reservoir may, unless indicated otherwise within the context of the invention, be performed using conventional techniques a description of which may be found, if needed, in specialist literature.

The compartment to which the apparatus that forms the subject of the invention applies is termed external in that it is distinct from the apparatus itself, even though it may be adjoining or sited remotely. It may for example be a container the purpose of which is to store and preserve products at a determined temperature, or at least with a narrow band of temperatures, while the temperature of the environment fluctuates widely. The term external compartment also encompasses a room or a building containing an atmospheric medium that needs to be made temperate (cooled or warmed as the case may be) using a climate-control device. The apparatus that forms the subject of the invention may thus be used to heat or cool a medium contained in an external compartment, with immediate or delayed action.

In the reactor according to the invention, at least one of the two bodies combined to constitute the enclosure thereof adopts the overall shape of a cap of circular or near-circular cross section. The cross section of the cap is said to be circular when the section passing through the top of said cap and perpendicular to the plane of the base thereof draws an arc of a circle. It is said to be near-circular when it draws an arc of an oval, an ellipse or a basket handle. In both instances, shapes exhibiting symmetry of revolution are preferred, for uniform load-distribution reasons. It will also be noted that the cross section of the cap may advantageously draw a semicircle, leading to a cap of hemispherical shape the base of which defines what is referred to as the “equatorial” plane of the reactor.

For the sake of clarity and simplicity the remainder of the present description will refer to hemispherical caps, although it must be understood that the similar shapes defined hereinabove are expressly included in the present invention.

Where two bodies in the form of caps are assembled, a reactor having a spherical enclosure is produced. When use is made of just one cap-shaped body, this will preferably be combined with a flat second body to produce a hemispherical enclosure. The reactor enclosure therefore has a mechanical strength that is optimized to cope with the stresses of the thermochemical reaction which involves high pressures. It is generally made of steel, stainless steel or composite material.

The reactor enclosure is thus made up of two bodies assembled, the cap-shaped body or bodies containing the reaction medium in the form of a block conforming to the overall shape of said cap. This block may be made as a single piece or of several smaller-sized blocks, but whatever the case, it is a solid element, pre-modeled to the space reserved for it inside the reactor body. It conforms to the overall shape of said cap without being fully imbricated therein, so as to leave space for the phenomena of expansion which may occur during operation of the reactor.

It is thus easy to place one or more blocks inside the cap before assembling the reactor enclosure. It is also easy to remove them when the two enclosure bodies are separated, so that they can be replaced or so that reactor maintenance can be carried out.

The two bodies of the enclosure are assembled by a flanged joint, this being equipped with clamping means (such as orifices for a bolted assembly, etc.) and sealing means, for example a seal made of EPDM (ethylene-propylene-diene monomer) elastomer, of graphite, or of any other material compatible with the reagents used. The flanged joint may be independent of the two bodies of the enclosure. It may, for example, clamp the two bodies together, these bodies then advantageously being provided with means for positioning said flanged joint.

On the other hand, it may form an integral part of the bodies of the reactor enclosure, in which case according to an advantageous feature of the apparatus that is the subject of the invention, the first and the second bodies respectively comprise a first and a second peripheral flange extending in an equatorial plane to constitute the halves of the flanged joint which are assembled by reversible clamping means, such as a nut and bolt assembly.

The reactor enclosure, which is obliged to be sealed, must, however, allow the circulation of the gaseous fluid between the reservoir and the reactor, via an inlet pipe opening into the reactor vessel, in the vicinity of the block of reactive medium. It must also make provision for the passage of a pipe from the heat-transfer means toward the external medium.

According to one advantageous embodiment of the apparatus that is the subject of the invention, the means of circulating the gaseous fluid between the reservoir and the reactor comprise a communication pipe entering the vessel between the first and the second flanges, which are held apart by spacer lips collaborating with the clamping means.

In another advantageous embodiment of the apparatus according to the invention, the heat-transfer means for transferring heat between the reactive medium and the external medium comprise a pipe entering the vessel between the first and the second flanges which are held apart by spacer lips collaborating with the clamping means.

The spacer lips may be machined at the base of the hemispherical body to ensure a sealed meeting of the two bodies of the enclosure in the equatorial plane (or the vicinity thereof). They have orifices fitted with seals needed for the passage of the communication and heat-transfer pipes.

In a different embodiment of the invention, the various pipes do not enter the reactor vessel via the equatorial zone at which the two bodies meet, but at various points through the enclosure. In that case, insofar as it is advantageous to increase the surface areas (for chemical and thermal) exchanges within the reactor, it is envisioned for several pipes to enter the reactor.

Thus, according to one particular embodiment of the apparatus that forms the subject of the invention, the means of circulating the gaseous fluid between the reservoir and the reactor comprise a communicating pipe that splits into a plurality of communication tubes, and the heat-transfer means for transferring heat between the reactive medium and the external medium comprise a heat-transfer pipe that splits into a plurality of heat-transfer tubes, said tubes entering the vessel through the reactor enclosure at various locations and extending along various axes inside said at least one block of reactive medium. The reactive block is pierced with passages designed to accept said communication and heat-transfer tubes. It is recommended that the axes along which these tubes enter be mutually parallel, so that when the system is being assembled or dismantled, they can all be engaged or disengaged by a simple translational movement along the axes of said passages.

The communication tubes entering the block of reactive medium are advantageously perforated so that they act as means of diffusing the gaseous fluid into and from the reactive medium. Perforations on a micrometric scale are created so that the gases are best distributed (and recovered), while at the same time holding back the particles which may become detached from the reactive block.

As explained previously, the reactor enclosure is formed of two bodies of which at least the first adopts the overall shape of a cap of circular or near-circular cross section. When the enclosure comprises a single cap-shaped body, the second body is preferably flat. Thus, according to one optional feature of the apparatus that forms the subject of the invention, the enclosure of the reactor is formed of two bodies assembled by a peripheral flanged joint, the first body adopting the overall shape of a cap of circular or near-circular cross-section, and the second body being in the form of a circular plate fitting the first body, the reactor containing a reactive medium formed of at least one block conforming to said overall shape of a cap. Advantageously, the plate has a diameter identical to the diameter of the base of the cap, so that it closes the first body. The hemisphere thus formed contains a block (of one piece or in several pieces) of reactive medium, which is itself hemispherical overall).

According to a preferred alternative form of embodiment of the apparatus that is the subject of the invention, the enclosure of the reactor is formed of two bodies assembled by a peripheral flanged joint, the first body and the second body each adopting the overall shape of a cap of circular or near-circular cross section fitting together and containing a reactive medium formed of at least two blocks each one conforming to said overall shape of a cap. Advantageously, the two caps have the same diameter, so that they close on one another, possibly with a spacer interposed between them. The sphere thus formed contains two blocks of reactive medium (as one piece or in several pieces), each hemispherical overall.

In this embodiment it is advantageous for the means that diffuse the gaseous fluid to be positioned in the equatorial part level with the communication pipe communicating with the fluid reservoir, and at the interface between the two blocks of reactive medium. This is why, according to one preferred feature of the invention, the diffusion means for diffusing the gaseous fluid comprise two perforated sheets extending in the equatorial plane of said cap-shaped bodies and separating the reactive blocks of each of said bodies of the reactor, the perforated sheets being fixed some distance apart so as to form an intermediate diffusion chamber between them.

The distance separating the two sheets may for example be at least equal to the height of the spacer lips. The sheets may have micro-perforations so as to create the means of diffusing the gas toward the reactive block, and of holding back the particles released, which carry the risk of causing the system to become clogged.

According to one advantageous feature of the invention, the perforated sheets of the intermediate chamber comprise a plurality of likewise perforated tubes which extend inside said blocks of reactive medium. For preference, they extend at regular intervals inside said blocks of reactive medium and with an orientation perpendicular to the equatorial plane of the reactor. This then scales down the chemical exchanges between the gas and the reactive salts, while allowing the reactor to be assembled by a simple translational movement of the members. For the reasons already mentioned, the tubes are pierced with micrometric-scale perforations.

According to another advantageous feature of the invention, the perforated sheets comprise a curved zone forming a central cavity in the intermediate chamber. This central cavity, which increases the volume of the intermediate chamber, is preferably substantially spherical. This then provides concentricity with the cap, making it possible to house a reactive medium of constant thickness in the vessel. This constitutes an advantage in optimizing the uniformity of the heat transfer, and also in using the reactive medium in the form of removable blocks.

The intermediate chamber thus created between the two sheets may advantageously be used to route and also house the reactor heating and cooling means (the heat-transfer means). It has been seen that the heat-transfer means may comprise a pipe entering the vessel between the first and the second flanges of the flanged joint. This feature is put to use for extending this heat transfer pipe into the intermediate chamber. There it may split into several tubules that penetrate the reactive block (after having passed through one or other of the sheets), so as to scale down the surface areas of exchange with the reactive medium. The heat-transfer means with which the apparatus according to the invention is equipped thus preferably comprise a plurality of tubules which extend through orifices made in said perforated sheets into said blocks of reactive medium. As before, and for the same reasons, an orientation perpendicular to the equatorial plane of the reactor and a distribution at regular intervals in the reactive block are preferred.

This then yields a system which, aside from the fact of being easy to dismantle, is also very efficient at removing the heat produced by the thermochemical reaction. Now, it has been seen that the cooling performance is essential to obtaining a good apparatus efficiency. This function, which was previously performed by limited, point to point electrical ventilation also subject to degradation in the environment of a thermochemical reactor, is now performed reliably and effectively by the reactor according to the invention.

In this context, it is still of course possible to use a conventional heat exchanger using the circulation of fluid, gas or liquid. However, for preference, the heat-transfer means comprise at least one heat-conducting element containing a pure fluid, also known as a heat pipe. A heat pipe is intended to transport heat using the principle of heat transfer through phase transition of a fluid (latent heat). Its benefit stems from its ability to amplify the cooling or the heating by influencing the permanent equilibrium between the liquid and vapor phases, the creation of a thermo siphon movement and the very high heat transfer coefficients so that heat can very rapidly be transferred from one point to another with heat exchange surface areas that may be small. For preference, said pure fluid of said heat pipe is chosen from pentane, methane and ethanol.

The reactor contains one or more solid blocks of reactive medium. According to one advantageous feature of the apparatus that is the subject of the present invention, the block of reactive medium consists of a composite material based on expanded natural graphite (ENG) and on a reactive salt chosen for example from barium chloride (BaCl2), calcium chloride (CaCl2), or manganese chloride (MnCl2), reacting with a suitable fluid, for example ammonia. Other reactive salts may also be used, notably chosen according to their enthalpy of reaction. A person skilled in the art will make a careful choice of fluid-reactive salts pairing, reacting with a fluid that changes state at a desired working temperature and pressure. A composite reactive medium of this type is known to those skilled in the art. It is particularly well suited to the device according to the invention, notably since it can be provided with the passages intended to accept the diffusion and heat transfer tubes as described above, by machining, or formed by pressing or stamping, etc.

Also, according to an advantageous feature of the apparatus that forms the subject of the present invention, said composite material has a layered structure, the layers being arranged along concentric surfaces that follow the cap shape of the body in which the block is housed. It is known that a layered structure can be obtained by mixing ENG with a salt then compressing the combination in a press designed for that purpose.

As explained previously, the orientation of the layers corresponds to the favored direction of heat transfer. In the preferred embodiment, because the layers are curved like the cap, heat transfers will essentially take place along spherical paths, toward the main pipe, encountering the heat-transfer tubes on the way so that the removal of heat is still further improved.

This curved-layers structure can be obtained according to the invention by performing uniaxial cold pressing of the composite in a press with a hemispherical bottom the size of which corresponding to that of a hemispherical body of the reactor. When use is further made of a rounded punch, the hemispherical block obtained has, at its base, a curved recess corresponding to the head of the punch, it advantageously being possible for this to be the size of a central cavity of the intermediate chamber. The thickness of the graphite/salt composite is therefore constant throughout the reactor.

As will be understood from reading the foregoing, the thermochemical system according to the invention offers significant improvements thanks to a reactor of an original, simple and effective design such that the manufacturing, assembly and maintenance operations become easier, with easy access to all the internal components. In the process, its efficiency is increased through an improved choice of size and therefore power and improved thermal and chemical exchanges.

The present invention will be better understood, and details thereof will become apparent, from the following description of alternative forms of embodiment thereof with reference to the attached figures in which:

FIG. 1 is a perspective view of a spherical reactor belonging to an apparatus according to the invention.

FIG. 2 is a view in section of the same spherical reactor.

FIG. 3 is a perspective view of a hemispherical reactor belonging to an apparatus according to the invention.

FIG. 4 is a view in section of the same hemispherical reactor.

EXAMPLE 1

FIGS. 1 and 2 depict a thermochemical reactor belonging to an apparatus for heating and/or cooling a medium external to the apparatus. The apparatus comprises a reactor 1, a reservoir (not depicted) containing a fluid capable of changing state (liquid or gaseous) in a determined range of temperatures and of pressures, and means for circulating the gaseous fluid between the reactor 1 and the reservoir.

The reactor 1 comprises two hemispherical bodies 111, 112 assembled by the peripheral flanged joint 3 and fitting together to form a rigid enclosure defining a vessel. The first and second bodies 111, 112 respectively comprise the first and second peripheral flanges 31 extending in an equatorial plane and constituting the halves of the flanged joint 3. The peripheral flanges 31 are assembled by removable clamping means 23, in this instance nuts and bolts.

The vessel contains a reactive medium capable of absorbing and desorbing the fluid in the gaseous state, for example ammonia, through a thermochemical reaction. The reactive medium is made for example as two blocks 12 of composite material based on expanded natural graphite and on barium chloride, conforming to the overall shape of the two hemispherical bodies. This composite material is structured as curved and concentric layers following the shape of the bodies 111 and 112 respectively in which the blocks 12 are housed.

Gaseous ammonia circulates between the reservoir and the reactor 1 by virtue of the communicating pipe 21 which enters the vessel between the first and second flanges 31. The flanges 31 are held spaced apart by spacer lips 22 collaborating with the clamping means 23 in order to seal the reactor 1.

The reactor comprises diffusing means 13 for diffusing said gaseous fluid into and from the reactive medium, which means are formed as follows. Two perforated sheets 16 extend in the equatorial plane of the bodies 111, 112 such that they separate the reactive blocks 12 of each of the bodies of the reactor 1. The perforated sheets 16 are fixed some distance apart at the level of the flange 31 so that the intermediate diffusion chamber 2 is formed between them. This chamber 2 occupies a “slice” of the reactor situated in an equatorial plane.

The perforated sheets 16 of the intermediate chamber 2 comprise a plurality of perforated tubes 171 (of which just one is visible for each sheet in the plane of section of FIG. 2), which extend into the blocks 12 of reactive medium. They further comprise a curved zone forming the central cavity 18 in the intermediate chamber 2.

The walls of the entire chamber with its tubes and its cavity are pierced with micro-perforations, of a diameter which may range from 10 μm to 100 μm.

The reactor also comprises heat-transfer means 14 for transferring heat between the reactive medium and the external medium. These comprise a pipe 15 entering the vessel between the first and second flanges 31. As a result, it enters the intermediate chamber 2, between the two sheets 16. This pipe comprises a plurality of tubules 172 which extend into the blocks 12 of reactive medium, having passed through orifices made in the perforated sheets 16. This entity constitutes a heat-conducting element containing a pure fluid, in this instance pentane which is well suited to the temperature ranges desired for refrigeration or climate control, and which is inexpensive and not overly corrosive.

EXAMPLE 2

FIGS. 3 and 4 depict another thermochemical reactor belonging to an apparatus for heating and/or cooling a medium external to the apparatus. The apparatus comprises a reactor 1, a reservoir (not depicted) containing a fluid able to change state (liquid or gaseous) in a determined range of temperature and pressures, and means of circulating the gaseous fluid between the reactor 1 and the reservoir.

The reactor 1 comprises a hemispherical body 112 and a flat body, namely the plate 113, which are assembled using the peripheral flanged joint 3. The bodies 112 and 113 fit together to form a rigid enclosure defining the reactor vessel. They respectively comprise the first and the second peripheral flanges 31 extending in an equatorial plane (defined with respect to the hemispherical body 112) and constituting the halves of the flanged joint 3. The peripheral flanges 31 are assembled contiguously by reversible clamping means 23, in this instance nuts and bolts.

The vessel contains a reactive medium capable of absorbing and desorbing the fluid in the gaseous state, for example ammonia, through a thermochemical reaction. The reactive medium is made of a block 12 of composite material based on expanded natural graphite and on barium chloride, conforming to the overall shape of the hemispherical body 112 and of the plate 113. This composite material is structured as curved and concentric layers following the shape of the body 112 in which the block 12 is housed.

The gaseous ammonia circulates between the reservoir and the reactor 1 along the communication pipe 21 which splits into two tubes 171, which enter the vessel through the hemispherical body 112 at two different locations and extend into the block 12 of reactive medium. The walls of the tubes are pierced with micro-perforations of a diameter which may range from 10 μm to 100 μm.

According to the same principle, the heat-transfer means 14 for transferring heat between the reactive medium and the external medium comprise a pipe 15 which splits into two tubes 172, which enter the vessel through the plate 113 at two different locations and extend along different axes inside the block 12 of reactive medium. This assembly constitutes a heat-conductive element containing a pure fluid, in this instance pentane. 

1. An apparatus for heating and/or cooling a medium contained in a compartment external to said apparatus, comprising i) a reactor (1), ii) a reservoir containing a liquid or gaseous fluid capable of changing state in a determined range of temperatures and of pressures, and iii) means of circulating the gaseous fluid between the reactor (1) and the reservoir, said reactor comprising: a rigid enclosure defining a vessel which contains a reactive medium able to absorb and desorb said fluid in the gaseous state through a thermochemical reaction, diffusing means (13) for diffusing said gaseous fluid into and from said reactive medium, heat-transfer means (14) for transferring heat between said reactive medium and said external medium, wherein the enclosure of the reactor (1) is formed of two bodies (11) assembled by a peripheral flanged joint (3), the first of which bodies at least adopts the overall shape of a cap of circular or near-circular cross section which contains said reactive medium in the form of at least one block (12) conforming to the overall shape of said cap.
 2. The apparatus as claimed in claim 1, wherein the first and the second bodies (11) respectively comprise a first and a second peripheral flange (31) extending in an equatorial plane to constitute the halves of the flanged joint (3) which are assembled by reversible clamping means (23).
 3. The apparatus as claimed in claim 1, wherein the means of circulating the gaseous fluid between the reservoir and the reactor (1) comprise a communication pipe (21) entering the vessel between the first and the second flanges (31), which are held apart by spacer lips (22) collaborating with the clamping means (23).
 4. The apparatus as claimed in claim 1, wherein the heat-transfer means (14) for transferring heat between the reactive medium and the external medium comprise a pipe (15) entering the vessel between the first and the second flanges (31) which are held apart by spacer lips (22) collaborating with the clamping means (23).
 5. The apparatus as claimed in claim 1, wherein the means of circulating the gaseous fluid between the reservoir and the reactor (1) comprise a communication pipe (21) that splits into a plurality of tubes (171), and the heat-transfer means (14) for transferring heat between the reactive medium and the external medium comprise a heat-transfer pipe (15) that splits into a plurality of tubes (172), said tubes (171, 172) entering the vessel through the enclosure at various locations and extending along various axes inside said at least one block (12) of reactive medium.
 6. The apparatus as claimed in claim 1, wherein the enclosure of the reactor (1) is formed of two bodies (11) assembled by a peripheral flanged joint (3), the first body (112) adopting the overall shape of a cap of circular or near-circular cross section, and the second body (113) being in the form of a circular plate fitting the first body, the reactor containing a reactive medium formed of at least one block (12) conforming to said overall shape of a cap.
 7. The apparatus as claimed in claim 1, wherein the enclosure of the reactor (1) is formed of two bodies (11) assembled by a peripheral flanged joint (3), the first body (111) and the second body (112) each adopting the overall shape of a cap of circular or near-circular cross section fitting together and containing a reactive medium formed of at least two blocks (12) each one conforming to said overall shape of a cap.
 8. The apparatus as claimed in claim 7, wherein the diffusion means (13) for diffusing the gaseous fluid comprise two perforated sheets (16) extending in the equatorial plane of said cap-shaped bodies (111, 112) and separating the reactive blocks (12) of each of said bodies of the reactor (1), the perforated sheets (16) being fixed some distance apart so as to form an intermediate diffusion chamber (2) between them.
 9. The apparatus as claimed in claim 8, wherein the perforated sheets (16) of the intermediate chamber (2) comprise a plurality of perforated tubes (171) which extend inside said blocks (12) of reactive medium.
 10. The apparatus as claimed in claim 8, wherein the perforated sheets (16) comprise a curved zone forming a central cavity (18) in the intermediate chamber (2).
 11. The apparatus as claimed in claim 8, wherein the heat-transfer means comprise a plurality of tubules (172) which extend through orifices made in said perforated sheets (16) into said blocks (12) of reactive medium.
 12. The apparatus as claimed in claim 11, wherein the heat-transfer means consist of at least one heat-conducting element containing a pure fluid, or heat pipe.
 13. The apparatus as claimed in claim 1, wherein the block (12) of reactive medium is made of a composite material based on expanded natural graphite and on a reactive salt, said composite material having a layered structure with the layers arranged along concentric surfaces that follow the shape of the cap-shaped body (11) in which the block (12) is housed.
 14. The apparatus as claimed in claim 2, wherein the means of circulating the gaseous fluid between the reservoir and the reactor (1) comprise a communication pipe (21) entering the vessel between the first and the second flanges (31), which are held apart by spacer lips (22) collaborating with the clamping means (23).
 15. The apparatus as claimed in claim 2, wherein the heat-transfer means (14) for transferring heat between the reactive medium and the external medium comprise a pipe (15) entering the vessel between the first and the second flanges (31) which are held apart by spacer lips (22) collaborating with the clamping means (23).
 16. The apparatus as claimed in claim 2, wherein the means of circulating the gaseous fluid between the reservoir and the reactor (1) comprise a communication pipe (21) that splits into a plurality of tubes (171), and the heat-transfer means (14) for transferring heat between the reactive medium and the external medium comprise a heat-transfer pipe (15) that splits into a plurality of tubes (172), said tubes (171, 172) entering the vessel through the enclosure at various locations and extending along various axes inside said at least one block (12) of reactive medium.
 17. The apparatus as claimed in claim 2, wherein the enclosure of the reactor (1) is formed of two bodies (11) assembled by a peripheral flanged joint (3), the first body (112) adopting the overall shape of a cap of circular or near-circular cross section, and the second body (113) being in the form of a circular plate fitting the first body, the reactor containing a reactive medium formed of at least one block (12) conforming to said overall shape of a cap.
 18. The apparatus as claimed in claim 1, wherein the enclosure of the reactor (1) is formed of two bodies (11) assembled by a peripheral flanged joint (3), the first body (111) and the second body (112) each adopting the overall shape of a cap of circular or near-circular cross section fitting together and containing a reactive medium formed of at least two blocks (12) each one conforming to said overall shape of a cap.
 19. The apparatus as claimed in claim 2, wherein the diffusion means (13) for diffusing the gaseous fluid comprise two perforated sheets (16) extending in the equatorial plane of said cap-shaped bodies (111, 112) and separating the reactive blocks (12) of each of said bodies of the reactor (1), the perforated sheets (16) being fixed some distance apart so as to form an intermediate diffusion chamber (2) between them.
 20. The apparatus as claimed in claim 9, wherein the perforated sheets (16) comprise a curved zone forming a central cavity (18) in the intermediate chamber (2). 